In the manufacture of large pallets of rigid plastics material and having recesses or spaces for receiving parallel spaced forks of a forklift truck, it is well known to form the pallets with a twin sheet thermoformed upper deck, for example, as disclosed in U.S. Pat. No. 5,197,396, No. 5,413,052, No. 5,676,064 and No. 5,813,355. It is also known to make or form upper decks and other components for a plastic pallet by extruding a plastic parison and directing the parison into blow molding equipment, for example, as disclosed in U.S. Pat. No. 5,845,588, No. 6,962,115 and No. 6,976,437. Blow-molding processes have also been used to form rigid hollow plastic panels, for example, as disclosed in U.S. Pat. No. 6,826,887. Plastic pallets have also been made by using injection molded components, for example, as disclosed in U.S. Pat. No. 6,389,990, No. 6,840,181 and No. 7,197,989. It is further known to make plastic pallets by rotational molding, for example, as disclosed in U.S. Pat. No. 6,807,911.
In the manufacture of any plastic pallet or hollow plastic panel, it is desirable to maximize the strength/weight ratio while minimizing the cost of manufacturing or producing the pallet or panel. Also, for many uses of a plastic pallet or panel, it is desirable for the top surface to be substantially smooth and solid without openings which can trap or collect undesirable debris or material. When the top deck and the bottom deck of a plastic pallet are vacuum-formed by a twin-sheet thermoforming process, it is also known to insert tubular metal reinforcing members between the sheets, for example, as disclosed in above mentioned U.S. Pat. No. 5,197,396 and No. 5,413,052. The top and bottom decks or panels of a plastic pallet formed by a twin-sheet or triple sheet thermoformed process are also commonly reinforced by vacuum-forming integral hollow or open ribs in the top and/or bottom sheets, for example, as disclosed in above U.S. Pat. No. 5,676,064, No. 5,813,355 and No. 6,749,418.